After reading Cesar Chavez Warns of Pesticide Risks, 1993, I couldn’t help but think of Rachel Carson and the legacy she left us with. Carson had curiosity in the relationship between environmental contamination and the safety of the public’s health. Like Chavez, she saw the deliberate disregard for the publics health, and the failure to inform the public about these potentially lethal, and hidden poisonings on earth. Her legacy was for this information to be accessible and that the people be given a chance to protect themselves.
We will never be able to release our carcinogenic burden, unless our industry, government, and society take on awareness and prevention. Either public or private sectors of our society need to try to prevent harm before it happens. Carcinogenic substances should not have to be taken out of the environment, because the truth should have been known prior to consideration of use. We should not to have to find a dead body to recognize a problem. It should be up to the manufacturers to tell us if a product is potentially dangerous. It should not have to be the citizens fighting to prove it to the manufacturers.
Carson spoke of the least toxic alternative as way of prevention. This means that if there is a less toxic alternative to a certain substance, regardless of cost, it should be used. But, to our industries, it is just not good business to act within these principals. It costs more money to look into possible health risks and to try to prevent such substances from hitting the market. Therefore, we as consumers are all being taken for a ride. Somehow in the course of our societies quest for more stuff, we forgot that it is the manufactures responsibility to inform and protect us from such things, not ours. But, in a consumer obsessed society, when there is a chance to make a buck, the concern for the public’s health doesn’t really matter. I think it is the reluctance of dominant social actors to do anything is the problem. “The chemical companies that manufacturer the pesticides and the growers who use them want us to believe that they are the health givers because of pesticides people are not dying of malaria or starvation. They have the politicians and government regulators that pesticides are a cure all- the key to an abundance of food” (Reader, pg. 142).
Our government is painting the wrong picture. They are saying that the lives that are being stolen by environmentally caused cancer, is a small price to pay when they are able to stop starvation. Chavez wrote his warnings of pesticide use 10 years ago. I would like to see how much the United States pesticide use has decreased the amounts of malaria and starvation in the world. If the government is slow to take action on these issues, it is up to us as a society to take a stand. Being aware and encouraging others to be informed, is a small effort to take to solve a huge problem. “Once social change begins, it can not be reversed. You can not uneducate the person who has learned to read…You can not oppress the people who are not afraid anymore” (Reader pg 142). Therefore, it is in our own hands to make the change we wish to see in the world. We must search for our ecological roots as a way of protecting ourselves from contamination.
When something that may be lethal to people is an actual possibility, then everyone has right to be informed. Citizens should no longer allow themselves to be lied to. We should be getting the correct information about anything concerning our health. For example, many people are unaware of how the incineration of product can affect a large amount of people. With the way that winds blow, and the distance these chemical clouds can travel, people for miles around an incineration site can be affected. All of these people have a right to know about what is going on, but instead, will never know at all. Therefore, I see it as our responsibility to make sure people know.
Some ways to achieve awareness and protection may be to get the information about the types of pesticides that have been locally sprayed. We would have to learn about the sources of drinking water and it’s quality, or learn about the way the winds blow across our towns and if they come from an industrial area. Another safety measure may be finding out about how our houses are fumigated, and the quality of the livestock we eat. All of these measures may be what might save our lives. Unfortunately we also live in a society that likes things to be done for us. As a result, many people will ignore warnings or won’t take the necessary precautions that could be what protects them. It is obvious to me now that putting all my eggs in one basket is not going to work. I am not going to rely on our Capitalist society, that is all about profit, to protect me from these silent killers that are still around us each day.
__________________
Warning!!! This is just a sample Pesticide Risks essay (Pesticide Risks essay example) writing service which provides college and university students with high-quality custom written essays, term papers, research papers, thesis papers and dissertations on Pesticide Risks topics.
Get professional Pesticide Risks essay writing help from our professional Ph.D. and Master's academic writers. A+ quality and 100% plagiarism are guaranteed! Feel free to ORDER A CUSTOM ESSAY ON PESTICIDE RISKS RIGHT NOW and you won't be disappointed.
Saturday, August 1, 2009
Ozone Depletion Essay
Above the earth, approximately 30-50 kilometers, a layer of stable oxygen atoms covers the stratosphere, this called the ozone layer. It protects “all life” from the sun’s harmful radiation. (US EPA). The ozone layer is very powerful; it protects the earth from dangerous UVB rays from the sun. (Frank 13) If the rays from the sun were to pass through the atmosphere it would be devastating because they have the ability to destroy skin cells in humans and animals. In 1974 two scientists discovered that certain commonly used compounds were destroying the protective ozone: chlorine, fluorine and bromine. Researchers have found out that the “stratospheric ozone has declined for at least two decades, with losses about 10% in the winter and spring, and 5% in the summer and autumn.” (Impacts of Depletion) As the ozone layer’s power is declining, more and more UVB rays are entering the atmosphere and eventually we will have no protection from the sun. “Since the 1980’s the annual ozone hole over Antarctica has been occurring only during the Antarctic spring.” (US EPA)
In the 1930s, commercial laboratories developed compounds of chlorine, fluorine, and carbon (called chlorofluorocarbons, or CFCs). (US EPA) These compounds can be found in normal household items such as refrigerators, spray cans, and air conditioners. (Frank 13) If such an item were used, CFCs would be released in the air and winds would carry them to the outer atmosphere of the Earth, the ozone layer. It is because of their “atmospheric lifetimes” that allow them time to reach the stratosphere. There they are broken down and release chlorine or bromine which then decomposes ozone molecules containing oxygen. CFCs are so stable that they can only be broken down by UVB radiation. This is one of the main reasons they were widely used. They are also nonflammable, and inexpensive to produce. (US EPA) According to studies, by the 1970s, industry used about a million tons each year. But CFCs aren’t the only cause of “atmospheric depression.” “Natural sources,” such as volcanic eruptions, also add to the destruction of the ozone layer even though their impact is not direct. Instead, they increase the rate at which the chlorine and bromine break down the ozone. (Impacts of Depletion). In fact, studies show that 85% of the chlorine found in the stratosphere is contributed by CFCs while “natural sources” contribute only 15%. (US EPA).
If in time the ozone layer does diminish or even disappear, the effects of UVB rays from the sun would be disastrous. Research shows that even a reduced amount of 7% of the “stratospheric ozone” could increase the number of cataracts in people exposed to the sun by 3% to 4%. The ultraviolet rays could create serious problems with the human skin, mainly affecting the DNA. If too many DNA cells are damaged, it can result in “faulty replication of DNA in a daughter cell.” That could cause important genes to malfunction, which could lead to tumors or cancer. The Sun’s rays would also harm the eyes because radiation is absorbed into the skin and outer areas of the eye. Because there is no discomfort or pain, it would be very easy to get long-term or even permanent damage to the eyes. Frank 16)
Because the ozone is depleting, there is a growing risk for people who stay in the sun. There are some helpful procedures you could do before you walk into the sun. Most important is using protective suntan lotion. You should always check the ‘sp’ or sun-proof strength to make sure that it is strong enough to last several hours. Sunglasses with UVB protective lenses are a very helpful accessory when driving or doing outdoor activities. Not only do they lower the risk of damage to your eyes but also they make you look good. Using common sense whenever you are outside is advisable. Don’t look directly into the sun. Don’t stay in the sun too long. You might think getting a tan looks good, but the radiation you receive from the sun can result in premature aging or skin cancer. So whenever you’re at the beach or swimming at a pool, take care of your skin to keep it in healthy condition.
The public really became aware of the destruction of the ozone layer due to CFCs in the 1970s when the US, Canada, Norway, and Sweden put a ban on the use of CFCs in aerosol sprays. In 1987, the Montreal Protocol was signed further reducing the production of CFCs. Many organizations, such as the Environmental Protection Agency (EPA), set out to help reduce “wear” on our ozone. The US EPA has created programs to help reduce the problem including refrigerant recycling and product labeling. With the continuing decrease of CFC use, the EPA has projected that “the natural ozone production process will heal the ozone layer in about 50 years.” (US EPA)
__________________
Warning!!! This is just a sample Ozone Depletion essay (Ozone Depletion essay example) writing service which provides college and university students with high-quality custom written essays, term papers, research papers, thesis papers and dissertations on Ozone Depletion topics.
Get professional Ozone Depletion essay writing help from our professional Ph.D. and Master's academic writers. A+ quality and 100% plagiarism are guaranteed! Feel free to ORDER A CUSTOM ESSAY ON OZONE DEPLETION RIGHT NOW and you won't be disappointed.
In the 1930s, commercial laboratories developed compounds of chlorine, fluorine, and carbon (called chlorofluorocarbons, or CFCs). (US EPA) These compounds can be found in normal household items such as refrigerators, spray cans, and air conditioners. (Frank 13) If such an item were used, CFCs would be released in the air and winds would carry them to the outer atmosphere of the Earth, the ozone layer. It is because of their “atmospheric lifetimes” that allow them time to reach the stratosphere. There they are broken down and release chlorine or bromine which then decomposes ozone molecules containing oxygen. CFCs are so stable that they can only be broken down by UVB radiation. This is one of the main reasons they were widely used. They are also nonflammable, and inexpensive to produce. (US EPA) According to studies, by the 1970s, industry used about a million tons each year. But CFCs aren’t the only cause of “atmospheric depression.” “Natural sources,” such as volcanic eruptions, also add to the destruction of the ozone layer even though their impact is not direct. Instead, they increase the rate at which the chlorine and bromine break down the ozone. (Impacts of Depletion). In fact, studies show that 85% of the chlorine found in the stratosphere is contributed by CFCs while “natural sources” contribute only 15%. (US EPA).
If in time the ozone layer does diminish or even disappear, the effects of UVB rays from the sun would be disastrous. Research shows that even a reduced amount of 7% of the “stratospheric ozone” could increase the number of cataracts in people exposed to the sun by 3% to 4%. The ultraviolet rays could create serious problems with the human skin, mainly affecting the DNA. If too many DNA cells are damaged, it can result in “faulty replication of DNA in a daughter cell.” That could cause important genes to malfunction, which could lead to tumors or cancer. The Sun’s rays would also harm the eyes because radiation is absorbed into the skin and outer areas of the eye. Because there is no discomfort or pain, it would be very easy to get long-term or even permanent damage to the eyes. Frank 16)
Because the ozone is depleting, there is a growing risk for people who stay in the sun. There are some helpful procedures you could do before you walk into the sun. Most important is using protective suntan lotion. You should always check the ‘sp’ or sun-proof strength to make sure that it is strong enough to last several hours. Sunglasses with UVB protective lenses are a very helpful accessory when driving or doing outdoor activities. Not only do they lower the risk of damage to your eyes but also they make you look good. Using common sense whenever you are outside is advisable. Don’t look directly into the sun. Don’t stay in the sun too long. You might think getting a tan looks good, but the radiation you receive from the sun can result in premature aging or skin cancer. So whenever you’re at the beach or swimming at a pool, take care of your skin to keep it in healthy condition.
The public really became aware of the destruction of the ozone layer due to CFCs in the 1970s when the US, Canada, Norway, and Sweden put a ban on the use of CFCs in aerosol sprays. In 1987, the Montreal Protocol was signed further reducing the production of CFCs. Many organizations, such as the Environmental Protection Agency (EPA), set out to help reduce “wear” on our ozone. The US EPA has created programs to help reduce the problem including refrigerant recycling and product labeling. With the continuing decrease of CFC use, the EPA has projected that “the natural ozone production process will heal the ozone layer in about 50 years.” (US EPA)
__________________
Warning!!! This is just a sample Ozone Depletion essay (Ozone Depletion essay example) writing service which provides college and university students with high-quality custom written essays, term papers, research papers, thesis papers and dissertations on Ozone Depletion topics.
Get professional Ozone Depletion essay writing help from our professional Ph.D. and Master's academic writers. A+ quality and 100% plagiarism are guaranteed! Feel free to ORDER A CUSTOM ESSAY ON OZONE DEPLETION RIGHT NOW and you won't be disappointed.
Friday, July 31, 2009
Hippocampus Essay
Through the studies of patients with hippocampus injury, it was revealed that the hippocampus helps with the formaton of declarative memories. For example, a patient whose initials are H. M. had severe epilepsy in which treatment consisted of the removal of the hippocampus. After the surgery was performed, it was clear that H. M. had a profound loss of memory for new events following the removal of the hippocampus. Although H. M was able to remember events prior the surgery, he was unable to form new memories and take in new facts into long term memory. One interesting note was that although his declarative memory was severely impaired, his procedural memory remained intact. This was discovered through a series of tasks administered to HM. One task was a mirror drawing task and required HM to draw a picture of an object from its mirror image. It was found that HM showed improvement in his drawing skills upon doing the task over a period of time, although HM denied any recollection of ever having done the task before. Moreover, HM was found to have a normal learning curve regarding the task, and retained his skills, regardless of his inability to remember the events. On another occasion, a psychologist had concealed a drawing pin in his hand and pricked HM as they shook hands. The following day, HM refused to shake the psychologist’s hand, although he denied he ever saw the psychologist before. Such observations are consistent with the associations that the hippocampus is necessary to form declarative, episodic memory. The hippocampus is thought to be associated with short term memory and in consolidating which episodic acts will be stored as long term memories.
Animal studies have shown that damage to the hippocampus hinders the learning process. For example, rats with removed hippocampi were unable to remember where they had or had not been, and hence were effectively hindered from learning a new maze. Such observations suggest that the hippocampus is needed in learning contextual or spatial information. In another study, it was found that monkeys with hippocampus damage were unable to navigate trhough once familiar areas. And in yet another study with monkeys, it was observed that destroying the hippocampus and amygdala, destroyed previous learning and prevented new learning from taking place.
From the observations with patients and animal studies alone, the important role of the hippocampus in memory and learning is quite obvious. However, the hippocampus is not the only area of the brain that accounts for the process of learning and memory storage as it seems that the hippocampus effects certain types of memory and learning more than others, such as declarive memory and spatial, contextual learning versus procedural tasks. The interplays of the hippocampus to other parts of the brain is an important area of study of memory and learning and much is still to researched and consolidated on the subject.
__________________
Warning!!! This is just a sample Hippocampus essay (Hippocampus essay example) writing service which provides college and university students with high-quality custom written essays, term papers, research papers, thesis papers and dissertations on Hippocampus topics.
Get professional Hippocampus essay writing help from our professional Ph.D. and Master's academic writers. A+ quality and 100% plagiarism are guaranteed! Feel free to ORDER A CUSTOM ESSAY ON HIPPOCAMPUS RIGHT NOW and you won't be disappointed.
Animal studies have shown that damage to the hippocampus hinders the learning process. For example, rats with removed hippocampi were unable to remember where they had or had not been, and hence were effectively hindered from learning a new maze. Such observations suggest that the hippocampus is needed in learning contextual or spatial information. In another study, it was found that monkeys with hippocampus damage were unable to navigate trhough once familiar areas. And in yet another study with monkeys, it was observed that destroying the hippocampus and amygdala, destroyed previous learning and prevented new learning from taking place.
From the observations with patients and animal studies alone, the important role of the hippocampus in memory and learning is quite obvious. However, the hippocampus is not the only area of the brain that accounts for the process of learning and memory storage as it seems that the hippocampus effects certain types of memory and learning more than others, such as declarive memory and spatial, contextual learning versus procedural tasks. The interplays of the hippocampus to other parts of the brain is an important area of study of memory and learning and much is still to researched and consolidated on the subject.
__________________
Warning!!! This is just a sample Hippocampus essay (Hippocampus essay example) writing service which provides college and university students with high-quality custom written essays, term papers, research papers, thesis papers and dissertations on Hippocampus topics.
Get professional Hippocampus essay writing help from our professional Ph.D. and Master's academic writers. A+ quality and 100% plagiarism are guaranteed! Feel free to ORDER A CUSTOM ESSAY ON HIPPOCAMPUS RIGHT NOW and you won't be disappointed.
Hodgkin's Disease Essay
Cancer is a disease that affects millions of people across the U.S. Hodgkin’s disease is one of its rare forms. Hodgkin’s disease is a lymphoma, characterized by an over abundance in the growth of Reed-Sternberg cells. This article will cover the ongoing research to find causes for Hodgkin’s disease in pediatric patients. Also to be discussed are the various stages of the disease and the correlation between its progression and treatment based upon a child’s developmental stage. Living with cancer during one’s youth can have lasting physical as well as psychological effects. In light of this, the frequency of late effects from both the illness itself and its treatment will be examined.
Hodgkin’s disease is responsible for 1% of pediatric cancer cases in the U.S. While cancer among children and adolescents is rare, the three most frequent major childhood cancers diagnosed over the course of a 21-year study conducted by the Surveillance, Epidemiology and End Results (SEER) Program were leukemias, CNS cancers and lymphomas with 4.4% being specified as Hodgkin’s disease. (1) Of all the childhood cancers examined in this study, which culminated in 1995, Hodgkin’s disease exhibited a modest, on a grand scale, but statistically significant decline thus allowing it to appear that all childhood lymphomas had decreased in occurrence. (1)
Incidence and Symptoms
There are no known causes for childhood Hodgkin’s. The general age distribution seems to have an early peak around the mid to late 20’s and a second around age 55 and older. Put simply, the potential for Hodgkin’s increases with age. In youths, onset of the disease is extremely rare in children under 5 years old. However it has a higher occurrence in males less than 10 years of age. About one third of cases in the United States have been associated with the presence of Epstein- Barr virus, commonly known as mononucleosis. Though it is not believed to be genetic, brothers and sisters of Hodgkin’s patients have a higher chance of developing the disease themselves. (1,4) During the course of the many years research devoted to Hodgkin’s by various oncology specialists a common challenge arises in terms of setting a concrete set of common risk factors of the disease. Many of the common factors within Hodgkin’s cases are found equally as often in persons without the disease. On the other hand, patients may develop the disease without any of the conditions believed to make one susceptible. Hodgkin’s is by no means communicable; it cannot be caught. The earliest symptoms of Hodgkin’s are much like that of a common cold or flu. The recurrence or persistence of these symptoms should alert the attending physician to test for the possible presence of Hodgkin’s.
Diagnosis/Staging
There are various methods of locating cancers in the body such as x-rays, a CT scan, or an MRI. However, the diagnosis of Hodgkin’s generally requires a lymph node biopsy to find the excessive Reed-Sternberg cells definitive of Hodgkin’s disease. When a patient’s biopsy is conclusive to Hodgkin’s disease, the process of clinical staging begins. Determination of the stage to which the disease has progressed is critical in choosing the proper method of treatment. In pediatric cases this often presents a challenge due to the highly invasive nature of clinical staging tests. Currently the standard clinical staging methods that include further CT scans of the chest, abdomen and pelvis, x-rays, and laboratory studies, are rarely included in the staging of children. (2) There are usually more false-positives in children than adults thus making the studies more difficult to perform. In the event that the initial biopsy is not conclusive, the steps of diagnosis and identifying the stage of the disease can be simultaneous. Under these circumstances the progression of the illness is still unknown and a patient may be at risk for cardiac arrest if placed under anesthesia, therefore a physician should consider a CT guided core needle biopsy.
Hodgkin’s disease is currently classified into four stages.
“These stages can be sub-classified into A and B categories and subcategory E: A for those patients who are asymptomatic and B for those patients with any of following specific symptoms:
-Unexplained loss of more than 10% of body weight in the 6 months before diagnosis
-Unexplained fever with temperatures above 38 degrees C for more than 3 days drenching night sweats”
The sub-classification E is reserved for confusing problems in staging resultant of extralymphatic disease. The E classification is not meant for widespread cases of Hodgkin’s that would fall under Stage IV.
The staging of Hodgkin’s disease has a stair-step progression of severity. Put simply the stage increases as the cancer increases the number lymph node regions in the body it effects. As the stages move up in severity of the disease not only lymph nodes but extralymphatic adjacent organs, such as the thymus, spleen, tonsils and bone marrow, are effected as well.
Treatment
When devising a treatment plan for pediatric Hodgkin’s patients a variety of factors must be considered. The age of the patient is among these, of course, but more specifically the developmental stage of the patient is considered. The methods used in treating adult cancers successfully, may have adverse affects upon a growing child. The most common methods include, radiation therapy, chemotherapy and bone marrow transplantation. The choice of which method is best truly depends upon the individual cases. In studies of late, the National Cancer Institute is attempting to limit the use of radiation in childhood cancers due the late effects it tends to have. *give an intro “Adolescents that have reached maximum growth but have localized childhood Hodgkin’s are treated as adults with standard radiation. For patients that have not yet reached their full growth chemotherapy along with involved-field radiation at lower dose is generally used.”(2)
Treatment of pediatric patients can most often result in a cure. However, in the event of relapse or in advanced stages of the disease the combination of chemotherapy along with another regimen has been known to produce prolonged remissions. Even so many survivors of childhood Hodgkin’s are met with late effects resulting from the treatment. Most often these occur in sexually mature male patients and in female patients from about age 10-16. In these incidences the ability to reproduce may be compromised. Male patients are encouraged to investigate storing sperm as treatment may leave them sterile; however this also presents a challenge as many have low sperm counts from the outset.
__________________
Warning!!! This is just a sample Hodgkin's disease essay (Hodgkin's disease essay example) writing service which provides college and university students with high-quality custom written essays, term papers, research papers, thesis papers and dissertations on Hodgkin's disease topics.
Get professional Hodgkin's disease essay writing help from our professional Ph.D. and Master's academic writers. A+ quality and 100% plagiarism are guaranteed! Feel free to ORDER A CUSTOM ESSAY ON HODGKIN'S DISEASE RIGHT NOW and you won't be disappointed.
Hodgkin’s disease is responsible for 1% of pediatric cancer cases in the U.S. While cancer among children and adolescents is rare, the three most frequent major childhood cancers diagnosed over the course of a 21-year study conducted by the Surveillance, Epidemiology and End Results (SEER) Program were leukemias, CNS cancers and lymphomas with 4.4% being specified as Hodgkin’s disease. (1) Of all the childhood cancers examined in this study, which culminated in 1995, Hodgkin’s disease exhibited a modest, on a grand scale, but statistically significant decline thus allowing it to appear that all childhood lymphomas had decreased in occurrence. (1)
Incidence and Symptoms
There are no known causes for childhood Hodgkin’s. The general age distribution seems to have an early peak around the mid to late 20’s and a second around age 55 and older. Put simply, the potential for Hodgkin’s increases with age. In youths, onset of the disease is extremely rare in children under 5 years old. However it has a higher occurrence in males less than 10 years of age. About one third of cases in the United States have been associated with the presence of Epstein- Barr virus, commonly known as mononucleosis. Though it is not believed to be genetic, brothers and sisters of Hodgkin’s patients have a higher chance of developing the disease themselves. (1,4) During the course of the many years research devoted to Hodgkin’s by various oncology specialists a common challenge arises in terms of setting a concrete set of common risk factors of the disease. Many of the common factors within Hodgkin’s cases are found equally as often in persons without the disease. On the other hand, patients may develop the disease without any of the conditions believed to make one susceptible. Hodgkin’s is by no means communicable; it cannot be caught. The earliest symptoms of Hodgkin’s are much like that of a common cold or flu. The recurrence or persistence of these symptoms should alert the attending physician to test for the possible presence of Hodgkin’s.
Diagnosis/Staging
There are various methods of locating cancers in the body such as x-rays, a CT scan, or an MRI. However, the diagnosis of Hodgkin’s generally requires a lymph node biopsy to find the excessive Reed-Sternberg cells definitive of Hodgkin’s disease. When a patient’s biopsy is conclusive to Hodgkin’s disease, the process of clinical staging begins. Determination of the stage to which the disease has progressed is critical in choosing the proper method of treatment. In pediatric cases this often presents a challenge due to the highly invasive nature of clinical staging tests. Currently the standard clinical staging methods that include further CT scans of the chest, abdomen and pelvis, x-rays, and laboratory studies, are rarely included in the staging of children. (2) There are usually more false-positives in children than adults thus making the studies more difficult to perform. In the event that the initial biopsy is not conclusive, the steps of diagnosis and identifying the stage of the disease can be simultaneous. Under these circumstances the progression of the illness is still unknown and a patient may be at risk for cardiac arrest if placed under anesthesia, therefore a physician should consider a CT guided core needle biopsy.
Hodgkin’s disease is currently classified into four stages.
“These stages can be sub-classified into A and B categories and subcategory E: A for those patients who are asymptomatic and B for those patients with any of following specific symptoms:
-Unexplained loss of more than 10% of body weight in the 6 months before diagnosis
-Unexplained fever with temperatures above 38 degrees C for more than 3 days drenching night sweats”
The sub-classification E is reserved for confusing problems in staging resultant of extralymphatic disease. The E classification is not meant for widespread cases of Hodgkin’s that would fall under Stage IV.
The staging of Hodgkin’s disease has a stair-step progression of severity. Put simply the stage increases as the cancer increases the number lymph node regions in the body it effects. As the stages move up in severity of the disease not only lymph nodes but extralymphatic adjacent organs, such as the thymus, spleen, tonsils and bone marrow, are effected as well.
Treatment
When devising a treatment plan for pediatric Hodgkin’s patients a variety of factors must be considered. The age of the patient is among these, of course, but more specifically the developmental stage of the patient is considered. The methods used in treating adult cancers successfully, may have adverse affects upon a growing child. The most common methods include, radiation therapy, chemotherapy and bone marrow transplantation. The choice of which method is best truly depends upon the individual cases. In studies of late, the National Cancer Institute is attempting to limit the use of radiation in childhood cancers due the late effects it tends to have. *give an intro “Adolescents that have reached maximum growth but have localized childhood Hodgkin’s are treated as adults with standard radiation. For patients that have not yet reached their full growth chemotherapy along with involved-field radiation at lower dose is generally used.”(2)
Treatment of pediatric patients can most often result in a cure. However, in the event of relapse or in advanced stages of the disease the combination of chemotherapy along with another regimen has been known to produce prolonged remissions. Even so many survivors of childhood Hodgkin’s are met with late effects resulting from the treatment. Most often these occur in sexually mature male patients and in female patients from about age 10-16. In these incidences the ability to reproduce may be compromised. Male patients are encouraged to investigate storing sperm as treatment may leave them sterile; however this also presents a challenge as many have low sperm counts from the outset.
__________________
Warning!!! This is just a sample Hodgkin's disease essay (Hodgkin's disease essay example) writing service which provides college and university students with high-quality custom written essays, term papers, research papers, thesis papers and dissertations on Hodgkin's disease topics.
Get professional Hodgkin's disease essay writing help from our professional Ph.D. and Master's academic writers. A+ quality and 100% plagiarism are guaranteed! Feel free to ORDER A CUSTOM ESSAY ON HODGKIN'S DISEASE RIGHT NOW and you won't be disappointed.
Thursday, July 30, 2009
History of Psychology Essay
Psychology on the whole deals with the nature of the mind and mental processes. Questions concerning these factors first came about from ancient Greek philosophers, the most famous being Socrates, Plato and Aristotle, during the forth and fifth centuries B.C. Hippocrates, was a Greek physician, frequently called the “father of medicine.” He was especially interested in the study of the living organism and its parts. He observed how the brain controlled various parts of the body. This gave rise to the biological perspective of psychology. Today, all new physicians reflect upon Hippocrates’s medical ethics for their study.
Following the Greek philosophers, around the 17th century, one of the discussions of human psychology was whether or not human beings are born with knowledge and understanding of reality, or are they acquired through experiences and interactions with the world. The view that we are born with existing knowledge is called the nativist view. The view that knowledge is gained through experiences is called the empiricist view. An English philosopher called John Locke, put forward a theory that at birth, the mind is at a blank slate, or tabula rasa, onto which experiences of what he/she sees, hears, smells, tastes and feels are written. In other words, there is no store of knowledge, but through our senses, our knowledge comes. Today it is still questionable and it is referred to as the nature versus nurture debate in psychology. It centres around the fact that biological processes affect our emotions and behaviour, but also acknowledges that experiences can also affect our behaviour.
In 1879, a man called Wilhelm Wundt (1832-1920) was considered by some to be the founder of modern psychology. Wundt was the leader of the school of structuralism, which contended that psychology is human experiences studied from the point of view of the person doing the experiencing. In other words, it was Wundt’s belief that the mind and behaviour can be subject to scientific analysis. Introspection and self-exploration are stressed. Introspection is referred to as the observations and recording of the nature of one’s own perceptions, thoughts and feelings. Structuralists in general, believed in the separation of mind and body, without interaction, but conceived of in such a way that a parallel structure is formed. For each conscious experience of the mind, a corresponding reaction occurs in the body. It must be remembered that the mind does not cause physical reactions any more than the body alters states of consciousness.
William James (1842-1910) brought about a new approach to psychology called functionalism. This refers to studying how the mind works so that an organism can adapt to and function in its environment. James established the first psychology laboratory in America. In the field of psychology, he is best known for his work, Principles of Psychology (1890), and his “stream-of-consciousness” belief that mentality must be seen as an ongoing process and not fragmented into bits of consciousness. James held that an emotion is evidenced by the internal conflict that arises from a person’s reaction to a particular emotional situation. Out of this theory grew his legendary argument that a man meeting a bear in the woods does not run because he is afraid, but rather is afraid because he runs. It is running itself that initiates the reaction of fear, which produces the emotion.
Watson John Broadus (1878-1958) was an American psychologist in favour of militant behaviourism. He says psychology is the ‘science of behaviour’. He believed human responses could be predicted by
• Observation
• Conditioned reflexes
• Verbal methods
• Testing
His studies of children and animals were innovative because structuralism and functionalists had virtually neglected these two groups. He worked on the conditioning of childhood fears and his advances with animals opened the way to the development of comparative psychology.
Around 1912, while behaviourism was appearing in the United States, Gestalt psychology was appearing in Germany. Gestalt being German for ‘form’ or ‘configuration.’ This approach was favoured by Max Wertheimer and basically contends that the psychological make-up of an individual is based on the unity and wholeness of behaviour, combined with experiences. In other words, Gestalt psychology is based on the concepts of unity and wholeness.
At the turn of the 20th century, psychoanalysis emerged. It originated from Sigmund Freud (1956-1939). His approach was based mainly on the unconscious, that is, the thoughts, attitudes, impulses, wishes, motivations and emotions which we are unaware of. Freud believed that these thoughts and feelings which we are forbidden of, leave our conscious state and enter the unconscious, but still continue to influence our thoughts and feelings. He says that these unconscious impulses are expressed in our dreams and physical mannerisms. Psychoanalysis is a psychological method that seeks the basis for human behaviour and motivation in the unconscious mind.
__________________
Warning!!! This is just a sample History of Psychology essay (History of Psychology essay example) writing service which provides college and university students with high-quality custom written essays, term papers, research papers, thesis papers and dissertations on History of Psychology topics.
Get professional History of Psychology essay writing help from our professional Ph.D. and Master's academic writers. A+ quality and 100% plagiarism are guaranteed! Feel free to ORDER A CUSTOM ESSAY ON HISTORY OF PSYCHOLOGY RIGHT NOW and you won't be disappointed.
Following the Greek philosophers, around the 17th century, one of the discussions of human psychology was whether or not human beings are born with knowledge and understanding of reality, or are they acquired through experiences and interactions with the world. The view that we are born with existing knowledge is called the nativist view. The view that knowledge is gained through experiences is called the empiricist view. An English philosopher called John Locke, put forward a theory that at birth, the mind is at a blank slate, or tabula rasa, onto which experiences of what he/she sees, hears, smells, tastes and feels are written. In other words, there is no store of knowledge, but through our senses, our knowledge comes. Today it is still questionable and it is referred to as the nature versus nurture debate in psychology. It centres around the fact that biological processes affect our emotions and behaviour, but also acknowledges that experiences can also affect our behaviour.
In 1879, a man called Wilhelm Wundt (1832-1920) was considered by some to be the founder of modern psychology. Wundt was the leader of the school of structuralism, which contended that psychology is human experiences studied from the point of view of the person doing the experiencing. In other words, it was Wundt’s belief that the mind and behaviour can be subject to scientific analysis. Introspection and self-exploration are stressed. Introspection is referred to as the observations and recording of the nature of one’s own perceptions, thoughts and feelings. Structuralists in general, believed in the separation of mind and body, without interaction, but conceived of in such a way that a parallel structure is formed. For each conscious experience of the mind, a corresponding reaction occurs in the body. It must be remembered that the mind does not cause physical reactions any more than the body alters states of consciousness.
William James (1842-1910) brought about a new approach to psychology called functionalism. This refers to studying how the mind works so that an organism can adapt to and function in its environment. James established the first psychology laboratory in America. In the field of psychology, he is best known for his work, Principles of Psychology (1890), and his “stream-of-consciousness” belief that mentality must be seen as an ongoing process and not fragmented into bits of consciousness. James held that an emotion is evidenced by the internal conflict that arises from a person’s reaction to a particular emotional situation. Out of this theory grew his legendary argument that a man meeting a bear in the woods does not run because he is afraid, but rather is afraid because he runs. It is running itself that initiates the reaction of fear, which produces the emotion.
Watson John Broadus (1878-1958) was an American psychologist in favour of militant behaviourism. He says psychology is the ‘science of behaviour’. He believed human responses could be predicted by
• Observation
• Conditioned reflexes
• Verbal methods
• Testing
His studies of children and animals were innovative because structuralism and functionalists had virtually neglected these two groups. He worked on the conditioning of childhood fears and his advances with animals opened the way to the development of comparative psychology.
Around 1912, while behaviourism was appearing in the United States, Gestalt psychology was appearing in Germany. Gestalt being German for ‘form’ or ‘configuration.’ This approach was favoured by Max Wertheimer and basically contends that the psychological make-up of an individual is based on the unity and wholeness of behaviour, combined with experiences. In other words, Gestalt psychology is based on the concepts of unity and wholeness.
At the turn of the 20th century, psychoanalysis emerged. It originated from Sigmund Freud (1956-1939). His approach was based mainly on the unconscious, that is, the thoughts, attitudes, impulses, wishes, motivations and emotions which we are unaware of. Freud believed that these thoughts and feelings which we are forbidden of, leave our conscious state and enter the unconscious, but still continue to influence our thoughts and feelings. He says that these unconscious impulses are expressed in our dreams and physical mannerisms. Psychoanalysis is a psychological method that seeks the basis for human behaviour and motivation in the unconscious mind.
__________________
Warning!!! This is just a sample History of Psychology essay (History of Psychology essay example) writing service which provides college and university students with high-quality custom written essays, term papers, research papers, thesis papers and dissertations on History of Psychology topics.
Get professional History of Psychology essay writing help from our professional Ph.D. and Master's academic writers. A+ quality and 100% plagiarism are guaranteed! Feel free to ORDER A CUSTOM ESSAY ON HISTORY OF PSYCHOLOGY RIGHT NOW and you won't be disappointed.
Atomic Theory Research Paper
Throughout the ages the study of what we call today chemistry has evolved into a highly developed point of study. One distinct element of chemistry is atomic theory. Throughout the ages atomic theory has been developed and extended by many different men who were all well-known chemists and physicists in their day. They developed the study of atoms from pure conjecture into known facts.
John Dalton originally was a schoolteacher in England. He thought about atoms as particles, which could make up the elements of our universe. Dalton reasoned about the nature of compounds, his theory became known as the “law of multiple proportions: when two elements form a series of compounds, the ratios of the masses of the second element that combine with one gram of the first element can always be reduced to small whole numbers” (43). Dalton created his theory on atoms and their nature. It was made up of four parts. First, “each element is made up of tiny particles called atoms.” Second, “The atoms of a given element are identical; the atoms of different elements are different in some fundamental way or ways.” Third, “chemical compounds are formed when atoms of different elements combine with each other. A given compound always has the same relative numbers and types of atoms.” Fourth, “chemical reactions involve reorganization of the atoms-changes in the way they are bound together. The atoms themselves are not changed in a chemical reaction.” Dalton, using the information that he had deduced and assumptions that he had made, created a table of the atomic masses, also known as atomic weights. Despite the fact that many of the masses on Dalton’s table were proved incorrect the creation of a table was a major step in the field of chemistry. (45)
The ideas and information that Dalton produced and showed to the scientific community was built upon in many ways by his successors. The aspect that was most developed by the scientists that followed Dalton was the periodic laws and the table that is organized based on those laws.
After [. . .] Dalton had developed the idea of atomic weights, chemists sought arithmetic connections between them, partly to see whether there was any likelihood of all elements being composed of a simple, common substance and partly to see whether occasional similarities in their properties pointed to similarities in structure. [. . .] Mendeleyev [. . .] formulated the periodic law, according to which, when all known elements are arranged in order of increasing atomic weight, the resulting table shows a periodicity of properties and allows one to observe the many types of chemical relation hitherto studied only in isolation. (Britannica)
At first, as any other scientific revolution, the scientific community did not accept Mendeleyev’s table when his laws were published in his book Principles of Chemistry (1868-1871). However, his periodic laws stood true to all elements of his time. Another interesting point is that since then many other elements have been discovered or created which all follow the same laws. Mendeleyev even left spaces for elements that were not known at the time foretelling that there were elements that had not been discovered when he died. Mendeleyev went so far as to predict the properties of many of the elements that he expected to be discovered. Today, the Periodic Table of the Elements looks very different and has many more elements on it but it still is based on the same laws, which is quite remarkable when one thinks about it. The periodic table is made up of transition metals, the representative elements, and the noble gases. The representative elements and the noble gases are organized into eight groups. These groups are organized based upon the number of valence electrons in the atom of that element. For example, oxygen has an electron configuration of [O] 1s2, 2s2, 2p4. The outer most orbital is the second, and there are six electrons in that orbital. The eighth group is Helium and the noble gases. The noble gases are very stable elements because they fill their subshells completely. They all end in a s2, p6, which fills the subshells. The other elements, the transition metals are set in the middle and the lanthanide series and actinide series are pulled out from the table for space reasons.
Joseph Gay-Lussac, a French chemist and physicist, used his experiments to decipher the means of determining the absolute formulas of compounds. The experiments that Gay-Lussac performed were mainly with gases. He worked with hydrogen and oxygen specifically. Gay-Lussac discovered that two quantities of hydrogen reacted with one quantity of oxygen, which formed two quantities of water vapor. Avogadro later used Gay-Lussac’s data when Avogadro formed his hypothesis.
Amodeo Avogadro, an Italian, worked towards discovering the means of determining the absolute formulas of compounds, as Gay-Lussac did. He used the data from Gay-Lussac’s experiments to postulate a hypothesis, known as Avogadro’s hypothesis. It read: “at the same temperature and pressure, equal volumes of different gases contain the same number of particles” (46). However, Avogadro’s deductions were ignored for fifty years before the chemistry community accepted his hypotheses.
William Crookes was another British scientist who helped the development of atomic theory. He developed atomic theory further through his cathode ray studies. Crookes’ experiments with cathode-ray tubes led him to show that when high-voltage electric current through the tube the tube glows. He also discovered that the cathode rays travel in straight lines. J.J. Thomson developed Crookes’ studies further a few years later.
J.J. Thomson, yet another Englishman, also worked on atomic theory. Thomson studied Crookes’ experiments and tested them. Thomson went on to discover that because the ray went from the negative cathode in the tube the ray must be negative. He also deduced that the ray was a stream of particles. Combining this deduction and his study that the ray went from negative to positive, he theorized that the stream must be a stream of negatively charged particles, now known as electrons. Thomson’s further studies allowed him to determine the ratio between the charge and mass of an electron, -1.76 X 108 C/g. Also from his experiments, Thomson discovered that all atoms must contain electrons. This must be true, he thought, because the rays occurred with various metals. Thomson is also known for his ‘plum pudding’ model of the atom. He believed that an atom was an amorphous mass in which there was no defined structure.
The New Zealand scientist that is notable for his work on atomic theory is Ernest Rutherford. Just after the turn of the twentieth century Rutherford was working on many experiments expanding on his predecessors. One of Rutherford’s most famous experiments was the one in which he tested Thomson’s ‘plum pudding’ model of the atom. Rutherford set up a device that aimed a particles at a thin metal foil with a screen encircling the metal foil meant to detect the a particles. According to Thomson’s belief the particles would all go right through the foil and hit the screen behind the metal foil. However, in the experiment when Rutherford sent the a particles at the metal foil the particles went in more than one direction. Many of them went right through the foil, however, some also were redirected when they contacted the metal foil. Knowing that electrons were negatively charged, Rutherford was able to hypothesize that there was a positively charged mass in the center of an atom, which he named the nucleus. However, many a particles still went through the foil, which told Rutherford that an atom had a great amount of empty space in its structure. Therefore, the structure was a relatively massive, positively charged center with electrons spread out throughout a large volume containing the extremely small electrons. Based on Thomson and Rutherford’s experimentation today we have developed a great deal of knowledge on the structure of an atom. We know that the atom is made up of negatively charged electrons which have almost no mass, neutral neutrons with a mass of about one atomic mass unit, and positively charged protons with a mass of about one atomic mass unit.
The German scientist, Max Planck, is also known for his advances in atomic theory. Planck studied the radiation given off by solid bodies that were heated to incandescence. Through Planck’s experimentation he discovered that matter could absorb or radiate any amount of energy. Planck explained his observations through an assumption “that energy can be gained or lost only in whole-number multiples” (295). The equation that went along with this assumption was DE=nhv, often used as DE=hv. In this equation DE is the change in energy, n is an integer, h is Planck’s constant (6.626 X 10-34 J-s), and v is the frequency of the electromagnetic radiation that is either absorbed or radiated. Before Planck’s experiments the belief of the scientific community was that the energy of matter did not change. Today based on Planck’s studies, we know that energy can only be found in certain quantities, the hv of Planck’s equation, which are now known as quanta (singular – quantum) which indicates that energy has separate properties from any other substance; this leads to quantum physics.
A notable Danish scientist, Neils Bohr, worked on atomic theory and is known for his model of the atom. Bohr offered a new idea. He stated “that the electron in a hydrogen atom moves around the nucleus only in certain allowed circular orbits” (301). This is known as the quantum model for the hydrogen atom. Through his knowledge of classical physics and its theories and some assumptions of his own he calculated the radii of the ‘allowed’ orbits of the electrons in a hydrogen atom. Bohr developed many ideas, which supported his quantum model. One of which asserts the energy levels available to the electron in the hydrogen atom. This equation is as follows: E=(-2.178 X 10-18J)(Z2/n2); the n is an integer (the larger the integer the larger the radius of the orbit) and Z is the charge of the nucleus.
Werner Heisenberg, a German, Louis de Broglie, a Frenchman, and Erwin Schrodinger, an Austrian, all worked towards a new model of the atom knowing that the Bohr model was not correct. These three men adopted a new path in the study of the atom. It is known as the wave, or quantum, mechanics theory. This resulted in yet another model of the atom. De Broglie discovered that the electron has wave properties. Schrodinger continued in this thought by trying to emphasize the wave properties of an atom. De Broglie and Schrodinger believed that the connection between the nucleus and an electron was comparable to a standing wave. Examples of standing waves include things like string instruments and so they studied standing waves and compared their findings to atomic structure. Schrodinger came up with an atom model that had electrons that behaved as if they were standing waves.
Schrodinger’s equation is: Hy=Ey; where y, called the wave function, is a function of the coordinates (x, y, and z) of the electron’s position in three-dimensional space and H represents a set of mathematical instructions called an operator. In this case, the operator contains mathematical terms that produce the total energy of the atom (the sum of the potential energy due to the attraction between the proton and electron and the kinetic energy of the moving electron). When this equation is analyzed, many solutions are found. Each solution consists of a wave function y that is characterized by a particular value of E. A specific wave function is often known as an orbital. (307)
When Schrodinger’s equation is solved the results show that there are many wave functions, orbitals, that are solutions. Every individual orbital is distinguished by quantum numbers, which can be deciphered so that the properties of the orbital are known. There are three kinds of quantum numbers: principal, angular momentum, and magnetic.
The principal quantum number (n) has integral values: 1, 2, and 3,…. The principal quantum number is related to the size and energy of the orbital. As n increases, the orbital becomes larger and the electron spends more time further from the nucleus. An increase in n also means higher energy, because the electron is less tightly bound to the nucleus and the energy is less negative.
The angular momentum quantum number (l) has integral values from 0 to (n – 1) for each value of n. This quantum number is related to the shape of atomic orbitals. The value of l for a particular orbital is commonly assigned a letter: l = 0 is called s; l = 1 is called p; l = 2 is called d; l = 3 is called f. This system arises from early spectral studies [. . .]. [l is also sometimes known as a subshell.]
The magnetic quantum number (ml) has integral values between l and –l, including 0. The value of ml is related to the orientation of the orbital in space relative to the other orbitals in the atom. (309-310)
Heisenberg’s discoveries added another twist to atomic theory, especially the wave, or quantum mechanics model. He concluded that “there is a fundamental limitation to just how precisely we can know both the position and momentum of a particle at a given time” (307). This is known as the Heisenberg uncertainty principle. Mathematically speaking it is shown as follows: “(Dx)[D(mv)]Ñ–[h/(4p)] where Dx is the uncertainty in a particle’s position, D(mv) is the uncertainty in a particle’s momentum, and h is Planck’s constant. Thus the minimum uncertainty in the equation is h/(4p)” (307). The only problem with the equation of the uncertainty principle is that the closer or more accurate a position measurement the more inaccurate the measurement of momentum is. When this principle is exercised in thinking about electrons it is shown that it is impossible for us to know the exact motion of an electron on its path around the nucleus. Therefore, Heisenberg disproves Bohr’s atomic model, a specified orbit, by his uncertainty principle.
The periodic table can be looked in blocks as well. The blocks are called the s-block, p-block, d-block, and f-block. These blocks have to do with the subshells of orbitals. Electrons fill up orbitals in order from 1 up. However, within these orbitals electrons fill up subshells. The subshells fill up in order from s, to p, to d, and then finally to f. The s subshell can hold up to two electrons, the p subshell can hold up to six electrons, the d subshell holds up to ten electrons, and the f subshell holds at maximum fourteen electrons. From left to right the first two vertical columns of elements and Helium are in the s-block because the last subshell in which electrons fall into is a s subshell. The p-block includes the elements in rest of the representative elements and the noble gases. The d-block includes all of the transition metals with exception of the lanthanide series and actinide series. The lanthanide series and actinide series are the elements in the f-block. These subshells fill in an order, which is shown in the aufbau principle.
From the work of the scientists who worked on atomic theory we know that electrons can be moved around between atoms. The atoms that lose an electron or electrons are called ions. Ionization energy is the energy needed to remove an electron from an atom so that the atom is at its considered ground state, forming a positive ion. An atom’s ground state is defined as the lowest possible energy state. There are two types of ionization energy: first and second ionization energy. First ionization energy is the energy need to remove the highest energy electron from an atom. Second ionization energy is much greater than first ionization energy and removes the next highest energy electron from the atom. This is true is because when an atom has a positive charge, after one electron has already been removed; the atom is bounded stronger than before. Therefore, more energy is necessary to remove a second electron from an atom. On the periodic table ionization energy reduces as one goes down a group of elements; for example, Helium has the highest ionization energy in the eighth group while Radon has the lowest. Also, as one moves from left to right ionization energy increases in most cases. For instance, Hydrogen has a lower ionization energy level than Helium. Electron affinity is the energy required for adding an electron to an atom, forming a negative ion. Generally, when going down a group on the periodic table electron affinity decreases, or gets closer to zero or more positive, but the differences are very small.
In conclusion, over many years scientists have developed atomic theory. However, it is all based on the things the early chemists did, including the experiments they performed and the information they passed on. In many respects, the early atomic theorists were the most important because they helped pave the way for the other scientists that continued to develop atomic theory.
__________________
Warning!!! This is just a sample Atomic Theory research paper (Atomic Theory research paper example) which cannot be used as your own paper. You can contact our custom research paper writing service which provides college and university students with high-quality custom written essays, term papers, research papers, thesis papers and dissertations on Atomic Theory topics.
Get professional Atomic Theory research paper writing help from our professional Ph.D. and Master's academic writers. A+ quality and 100% plagiarism are guaranteed! Feel free to ORDER A CUSTOM RESEARCH PAPER ON ATOMIC THEORY RIGHT NOW and you won't be disappointed.
John Dalton originally was a schoolteacher in England. He thought about atoms as particles, which could make up the elements of our universe. Dalton reasoned about the nature of compounds, his theory became known as the “law of multiple proportions: when two elements form a series of compounds, the ratios of the masses of the second element that combine with one gram of the first element can always be reduced to small whole numbers” (43). Dalton created his theory on atoms and their nature. It was made up of four parts. First, “each element is made up of tiny particles called atoms.” Second, “The atoms of a given element are identical; the atoms of different elements are different in some fundamental way or ways.” Third, “chemical compounds are formed when atoms of different elements combine with each other. A given compound always has the same relative numbers and types of atoms.” Fourth, “chemical reactions involve reorganization of the atoms-changes in the way they are bound together. The atoms themselves are not changed in a chemical reaction.” Dalton, using the information that he had deduced and assumptions that he had made, created a table of the atomic masses, also known as atomic weights. Despite the fact that many of the masses on Dalton’s table were proved incorrect the creation of a table was a major step in the field of chemistry. (45)
The ideas and information that Dalton produced and showed to the scientific community was built upon in many ways by his successors. The aspect that was most developed by the scientists that followed Dalton was the periodic laws and the table that is organized based on those laws.
After [. . .] Dalton had developed the idea of atomic weights, chemists sought arithmetic connections between them, partly to see whether there was any likelihood of all elements being composed of a simple, common substance and partly to see whether occasional similarities in their properties pointed to similarities in structure. [. . .] Mendeleyev [. . .] formulated the periodic law, according to which, when all known elements are arranged in order of increasing atomic weight, the resulting table shows a periodicity of properties and allows one to observe the many types of chemical relation hitherto studied only in isolation. (Britannica)
At first, as any other scientific revolution, the scientific community did not accept Mendeleyev’s table when his laws were published in his book Principles of Chemistry (1868-1871). However, his periodic laws stood true to all elements of his time. Another interesting point is that since then many other elements have been discovered or created which all follow the same laws. Mendeleyev even left spaces for elements that were not known at the time foretelling that there were elements that had not been discovered when he died. Mendeleyev went so far as to predict the properties of many of the elements that he expected to be discovered. Today, the Periodic Table of the Elements looks very different and has many more elements on it but it still is based on the same laws, which is quite remarkable when one thinks about it. The periodic table is made up of transition metals, the representative elements, and the noble gases. The representative elements and the noble gases are organized into eight groups. These groups are organized based upon the number of valence electrons in the atom of that element. For example, oxygen has an electron configuration of [O] 1s2, 2s2, 2p4. The outer most orbital is the second, and there are six electrons in that orbital. The eighth group is Helium and the noble gases. The noble gases are very stable elements because they fill their subshells completely. They all end in a s2, p6, which fills the subshells. The other elements, the transition metals are set in the middle and the lanthanide series and actinide series are pulled out from the table for space reasons.
Joseph Gay-Lussac, a French chemist and physicist, used his experiments to decipher the means of determining the absolute formulas of compounds. The experiments that Gay-Lussac performed were mainly with gases. He worked with hydrogen and oxygen specifically. Gay-Lussac discovered that two quantities of hydrogen reacted with one quantity of oxygen, which formed two quantities of water vapor. Avogadro later used Gay-Lussac’s data when Avogadro formed his hypothesis.
Amodeo Avogadro, an Italian, worked towards discovering the means of determining the absolute formulas of compounds, as Gay-Lussac did. He used the data from Gay-Lussac’s experiments to postulate a hypothesis, known as Avogadro’s hypothesis. It read: “at the same temperature and pressure, equal volumes of different gases contain the same number of particles” (46). However, Avogadro’s deductions were ignored for fifty years before the chemistry community accepted his hypotheses.
William Crookes was another British scientist who helped the development of atomic theory. He developed atomic theory further through his cathode ray studies. Crookes’ experiments with cathode-ray tubes led him to show that when high-voltage electric current through the tube the tube glows. He also discovered that the cathode rays travel in straight lines. J.J. Thomson developed Crookes’ studies further a few years later.
J.J. Thomson, yet another Englishman, also worked on atomic theory. Thomson studied Crookes’ experiments and tested them. Thomson went on to discover that because the ray went from the negative cathode in the tube the ray must be negative. He also deduced that the ray was a stream of particles. Combining this deduction and his study that the ray went from negative to positive, he theorized that the stream must be a stream of negatively charged particles, now known as electrons. Thomson’s further studies allowed him to determine the ratio between the charge and mass of an electron, -1.76 X 108 C/g. Also from his experiments, Thomson discovered that all atoms must contain electrons. This must be true, he thought, because the rays occurred with various metals. Thomson is also known for his ‘plum pudding’ model of the atom. He believed that an atom was an amorphous mass in which there was no defined structure.
The New Zealand scientist that is notable for his work on atomic theory is Ernest Rutherford. Just after the turn of the twentieth century Rutherford was working on many experiments expanding on his predecessors. One of Rutherford’s most famous experiments was the one in which he tested Thomson’s ‘plum pudding’ model of the atom. Rutherford set up a device that aimed a particles at a thin metal foil with a screen encircling the metal foil meant to detect the a particles. According to Thomson’s belief the particles would all go right through the foil and hit the screen behind the metal foil. However, in the experiment when Rutherford sent the a particles at the metal foil the particles went in more than one direction. Many of them went right through the foil, however, some also were redirected when they contacted the metal foil. Knowing that electrons were negatively charged, Rutherford was able to hypothesize that there was a positively charged mass in the center of an atom, which he named the nucleus. However, many a particles still went through the foil, which told Rutherford that an atom had a great amount of empty space in its structure. Therefore, the structure was a relatively massive, positively charged center with electrons spread out throughout a large volume containing the extremely small electrons. Based on Thomson and Rutherford’s experimentation today we have developed a great deal of knowledge on the structure of an atom. We know that the atom is made up of negatively charged electrons which have almost no mass, neutral neutrons with a mass of about one atomic mass unit, and positively charged protons with a mass of about one atomic mass unit.
The German scientist, Max Planck, is also known for his advances in atomic theory. Planck studied the radiation given off by solid bodies that were heated to incandescence. Through Planck’s experimentation he discovered that matter could absorb or radiate any amount of energy. Planck explained his observations through an assumption “that energy can be gained or lost only in whole-number multiples” (295). The equation that went along with this assumption was DE=nhv, often used as DE=hv. In this equation DE is the change in energy, n is an integer, h is Planck’s constant (6.626 X 10-34 J-s), and v is the frequency of the electromagnetic radiation that is either absorbed or radiated. Before Planck’s experiments the belief of the scientific community was that the energy of matter did not change. Today based on Planck’s studies, we know that energy can only be found in certain quantities, the hv of Planck’s equation, which are now known as quanta (singular – quantum) which indicates that energy has separate properties from any other substance; this leads to quantum physics.
A notable Danish scientist, Neils Bohr, worked on atomic theory and is known for his model of the atom. Bohr offered a new idea. He stated “that the electron in a hydrogen atom moves around the nucleus only in certain allowed circular orbits” (301). This is known as the quantum model for the hydrogen atom. Through his knowledge of classical physics and its theories and some assumptions of his own he calculated the radii of the ‘allowed’ orbits of the electrons in a hydrogen atom. Bohr developed many ideas, which supported his quantum model. One of which asserts the energy levels available to the electron in the hydrogen atom. This equation is as follows: E=(-2.178 X 10-18J)(Z2/n2); the n is an integer (the larger the integer the larger the radius of the orbit) and Z is the charge of the nucleus.
Werner Heisenberg, a German, Louis de Broglie, a Frenchman, and Erwin Schrodinger, an Austrian, all worked towards a new model of the atom knowing that the Bohr model was not correct. These three men adopted a new path in the study of the atom. It is known as the wave, or quantum, mechanics theory. This resulted in yet another model of the atom. De Broglie discovered that the electron has wave properties. Schrodinger continued in this thought by trying to emphasize the wave properties of an atom. De Broglie and Schrodinger believed that the connection between the nucleus and an electron was comparable to a standing wave. Examples of standing waves include things like string instruments and so they studied standing waves and compared their findings to atomic structure. Schrodinger came up with an atom model that had electrons that behaved as if they were standing waves.
Schrodinger’s equation is: Hy=Ey; where y, called the wave function, is a function of the coordinates (x, y, and z) of the electron’s position in three-dimensional space and H represents a set of mathematical instructions called an operator. In this case, the operator contains mathematical terms that produce the total energy of the atom (the sum of the potential energy due to the attraction between the proton and electron and the kinetic energy of the moving electron). When this equation is analyzed, many solutions are found. Each solution consists of a wave function y that is characterized by a particular value of E. A specific wave function is often known as an orbital. (307)
When Schrodinger’s equation is solved the results show that there are many wave functions, orbitals, that are solutions. Every individual orbital is distinguished by quantum numbers, which can be deciphered so that the properties of the orbital are known. There are three kinds of quantum numbers: principal, angular momentum, and magnetic.
The principal quantum number (n) has integral values: 1, 2, and 3,…. The principal quantum number is related to the size and energy of the orbital. As n increases, the orbital becomes larger and the electron spends more time further from the nucleus. An increase in n also means higher energy, because the electron is less tightly bound to the nucleus and the energy is less negative.
The angular momentum quantum number (l) has integral values from 0 to (n – 1) for each value of n. This quantum number is related to the shape of atomic orbitals. The value of l for a particular orbital is commonly assigned a letter: l = 0 is called s; l = 1 is called p; l = 2 is called d; l = 3 is called f. This system arises from early spectral studies [. . .]. [l is also sometimes known as a subshell.]
The magnetic quantum number (ml) has integral values between l and –l, including 0. The value of ml is related to the orientation of the orbital in space relative to the other orbitals in the atom. (309-310)
Heisenberg’s discoveries added another twist to atomic theory, especially the wave, or quantum mechanics model. He concluded that “there is a fundamental limitation to just how precisely we can know both the position and momentum of a particle at a given time” (307). This is known as the Heisenberg uncertainty principle. Mathematically speaking it is shown as follows: “(Dx)[D(mv)]Ñ–[h/(4p)] where Dx is the uncertainty in a particle’s position, D(mv) is the uncertainty in a particle’s momentum, and h is Planck’s constant. Thus the minimum uncertainty in the equation is h/(4p)” (307). The only problem with the equation of the uncertainty principle is that the closer or more accurate a position measurement the more inaccurate the measurement of momentum is. When this principle is exercised in thinking about electrons it is shown that it is impossible for us to know the exact motion of an electron on its path around the nucleus. Therefore, Heisenberg disproves Bohr’s atomic model, a specified orbit, by his uncertainty principle.
The periodic table can be looked in blocks as well. The blocks are called the s-block, p-block, d-block, and f-block. These blocks have to do with the subshells of orbitals. Electrons fill up orbitals in order from 1 up. However, within these orbitals electrons fill up subshells. The subshells fill up in order from s, to p, to d, and then finally to f. The s subshell can hold up to two electrons, the p subshell can hold up to six electrons, the d subshell holds up to ten electrons, and the f subshell holds at maximum fourteen electrons. From left to right the first two vertical columns of elements and Helium are in the s-block because the last subshell in which electrons fall into is a s subshell. The p-block includes the elements in rest of the representative elements and the noble gases. The d-block includes all of the transition metals with exception of the lanthanide series and actinide series. The lanthanide series and actinide series are the elements in the f-block. These subshells fill in an order, which is shown in the aufbau principle.
From the work of the scientists who worked on atomic theory we know that electrons can be moved around between atoms. The atoms that lose an electron or electrons are called ions. Ionization energy is the energy needed to remove an electron from an atom so that the atom is at its considered ground state, forming a positive ion. An atom’s ground state is defined as the lowest possible energy state. There are two types of ionization energy: first and second ionization energy. First ionization energy is the energy need to remove the highest energy electron from an atom. Second ionization energy is much greater than first ionization energy and removes the next highest energy electron from the atom. This is true is because when an atom has a positive charge, after one electron has already been removed; the atom is bounded stronger than before. Therefore, more energy is necessary to remove a second electron from an atom. On the periodic table ionization energy reduces as one goes down a group of elements; for example, Helium has the highest ionization energy in the eighth group while Radon has the lowest. Also, as one moves from left to right ionization energy increases in most cases. For instance, Hydrogen has a lower ionization energy level than Helium. Electron affinity is the energy required for adding an electron to an atom, forming a negative ion. Generally, when going down a group on the periodic table electron affinity decreases, or gets closer to zero or more positive, but the differences are very small.
In conclusion, over many years scientists have developed atomic theory. However, it is all based on the things the early chemists did, including the experiments they performed and the information they passed on. In many respects, the early atomic theorists were the most important because they helped pave the way for the other scientists that continued to develop atomic theory.
__________________
Warning!!! This is just a sample Atomic Theory research paper (Atomic Theory research paper example) which cannot be used as your own paper. You can contact our custom research paper writing service which provides college and university students with high-quality custom written essays, term papers, research papers, thesis papers and dissertations on Atomic Theory topics.
Get professional Atomic Theory research paper writing help from our professional Ph.D. and Master's academic writers. A+ quality and 100% plagiarism are guaranteed! Feel free to ORDER A CUSTOM RESEARCH PAPER ON ATOMIC THEORY RIGHT NOW and you won't be disappointed.
Wednesday, July 29, 2009
Pay for Research Paper
Have you ever enjoyed custom research paper writing services? Have you ever ordered custom research papers? Have you ever needed professional research paper help provided by qualified academic writers? If so, you know exactly that you need to pay for such writing services. If you are willing to pay for custom research paper writing you have to contact decent and reliable research paper companies to have your paper made by professional Ph.D. and Master’s writers. But which services you should pay to get a high-quality custom research paper? Which companies employ highly-qualified and certified writers to produce A+ quality custom written papers requested by customers?
There are thousands of research paper agencies which can provide you with quality writing services. Are you ready to pay for such services? Feel free to contact professional research paper services at which you can buy high-quality custom papers. Actually, free sample research papers and research paper examples which can be found everywhere online are not so effective as custom research papers. There are also various tutorials and guidelines on how to prepare good research papers, how to edit/proofread research papers and how to format them in the best way, - but all these tips cannot provide students with custom works.
Our company can gladly offer you top-quality research paper writing services which are designed to help students with writing their academic research papers assigned in school, high school, college and university. All our research paper writing company affiliates with such worldwide online payment systems as Pay Pal, 2 Check Out, Western Union and Money Bookers. So you won’t need to worry about confidentiality and security – we don’t disclose any private information to third party agencies. Everything is guaranteed by our company: superior quality, no plagiarism, on-time delivery, authenticity.
For 4 years of its existence our company has already helped millions of students with writing research papers, essays, term papers and dissertations on different topics and in any disciplines. We have already written billions of research papers in Law, English, Marketing, Business, Management, Economics, Literature, Finance, Nursing, Accounting, Sociology, History, Education, Art, Philosophy, Political science, Psychology, Computer science, Engineering, Medical studies, Sports, Music, Media studies, Ecology, Physics, Mathematics, Chemistry, Geology, Biology, Criminology, Geography etc.
Feel free to pay a fair price for our custom research paper services which will never let you down regarding writing papers on any topic, in any discipline and in any citation style: MLA, APA, Harvard or Turabian/Chicago format. If you make your mind to pay someone to write your research paper – contact us and we will help write your paper of any complexity as we never drop huge assignments. If you pay us for writing your research paper you can be 100% certain that your will get a 100% custom research paper written by professional academic freelance writers. PAY FOR YOUR CUSTOM RESEARCH PAPER NOW and you will understand that our company is the best research paper writing company on the market.
There are thousands of research paper agencies which can provide you with quality writing services. Are you ready to pay for such services? Feel free to contact professional research paper services at which you can buy high-quality custom papers. Actually, free sample research papers and research paper examples which can be found everywhere online are not so effective as custom research papers. There are also various tutorials and guidelines on how to prepare good research papers, how to edit/proofread research papers and how to format them in the best way, - but all these tips cannot provide students with custom works.
Our company can gladly offer you top-quality research paper writing services which are designed to help students with writing their academic research papers assigned in school, high school, college and university. All our research paper writing company affiliates with such worldwide online payment systems as Pay Pal, 2 Check Out, Western Union and Money Bookers. So you won’t need to worry about confidentiality and security – we don’t disclose any private information to third party agencies. Everything is guaranteed by our company: superior quality, no plagiarism, on-time delivery, authenticity.
For 4 years of its existence our company has already helped millions of students with writing research papers, essays, term papers and dissertations on different topics and in any disciplines. We have already written billions of research papers in Law, English, Marketing, Business, Management, Economics, Literature, Finance, Nursing, Accounting, Sociology, History, Education, Art, Philosophy, Political science, Psychology, Computer science, Engineering, Medical studies, Sports, Music, Media studies, Ecology, Physics, Mathematics, Chemistry, Geology, Biology, Criminology, Geography etc.
Feel free to pay a fair price for our custom research paper services which will never let you down regarding writing papers on any topic, in any discipline and in any citation style: MLA, APA, Harvard or Turabian/Chicago format. If you make your mind to pay someone to write your research paper – contact us and we will help write your paper of any complexity as we never drop huge assignments. If you pay us for writing your research paper you can be 100% certain that your will get a 100% custom research paper written by professional academic freelance writers. PAY FOR YOUR CUSTOM RESEARCH PAPER NOW and you will understand that our company is the best research paper writing company on the market.
Subscribe to:
Posts (Atom)